?php
class Mysql{
     private static $host="localhost";
     private static $user="root";
     private static $password="123456";
     private static $dbName="test";           //数据库名
     private static $charset="utf8";          //字符编码
     private static $port="3306";            //端口号
     private $conn=null;
     function __construct(){
       $this->conn=new mysqli(self::$host,self::$user,self::$password,self::$dbName,self::$port);
       if(!$this->conn)
       {
          die("数据库连接失败！".$this->conn->connect_error);
       }else{
         echo "连接成功！";
       }
       $this->conn->query("set names ".self::$charset);
     }
     //执行sql语句
     function sql($sql){
       $res=$this->conn->query($sql);
     if(!$res)
       {
          echo "数据操作失败";
       }
       else
       {
          if($this->conn->affected_rows>0)
          {
             return $res;
          }
          else
          {
            echo "0行数据受影响！";
          }
       }
     }
     //返回受影响数据行数
     function getResultNum($sql){
      $res=$this->conn->query($sql);
      return mysqli_num_rows($res);
      }
     //关闭数据库
     public function close()
     {
       @mysqli_close($this->conn);
     }
}
?>

?php
require_once "mysql.php";
$conn=new Mysql();
$sql="select * from user";
//执行查询并获取查询结果
$result=$conn->sql($sql);
//输出受影响数据行数
$num=$conn->getResultNum($sql);
echo "影响的行数：".$num;
//读取并输出记录
while ($row = mysqli_fetch_assoc($result))
{
  echo "{$row['name']} ";
  echo "{$row['password']}";
}
//关闭数据库
$conn->close();